It is essential for early diagnosis of disease or accurate analysis of pathology, to determine quantitatively the amounts of biomolecules, such as cytokines, hormones, proteins and nucleic acids, contained in body fluids such as blood plasma, lymph and tissue fluid or to detect the trace amounts of biomolecules contained in the body fluids. An ELISA method, a chemoluminescence method or a bead assay by a flow cytometer is mainly practiced for quantitative determination or detection of biomolecules.
However, the ELISA and chemoluminescence methods, which detect only a single kind of biomolecule in a single reaction, unfavorably demanded an extended period and larger labor for detection of plural biomolecules and increase in cost, because the sample and the reagent are needed in greater amounts.
Bead assays by using a flow cytometer have been attracting attention recently as a method of quantitative determining plural kinds of biomolecules in a single operation (see e.g., Non-patent Document 1). The beads used in conventional bead assays are fluorescent-labelled polymer beads that have functional groups introduced onto the surface by surface treatment, which are additionally bound to biomolecules. Production of such beads demand sophisticated technique and tedious operation, making the beads very expensive.
[Non-patent Document 1] J. Immunological Methods 2001, 254, 109-118